North Korea’s detonation of hydrogen bomb Sunday is being considered the most powerful out of the six nuclear tests the country has ever conducted.

Fearfully, however, a mountain in North Korea believed to be the site of the supposed hydrogen bomb explosion is at risk of collapsing and leaking radiation into the region.

Experts say if the peak crumbles, clouds of radioactive dust and gas will blanket the region.

According to a geophysicist, Wen Lianxing and his team at the University of Science and Technology of China in Hefei, Anhui province, they “were confident” underground detonations were occurring underneath the mountain.

A hydrogen bomb is a highly sophisticated weapon capable of achieving thousands of kilotons of explosive yield. It is considered much deadlier and more devastating compared to a standard nuclear bomb.

Conversely, according to Alex Wellerstein’s NukeMap, an attack with such a weapon 1km above the tower would cause 65,000 casualties and more than 120,000 injuries.